Urea, subject to high N losses, is the predominant N fertilizer used for perennial forage grass production in Ontario/Canada. Application of all N to grasses from a more stable N source such as ammonium sulphate could be costly. Blends of the two fertilizers could work better than either of the two fertilizers. A field experiment in completely randomized block design, replicated four times, to evaluate comparative performance of urea, ammonium sulphate and their blends (80:20, 60:40, 40:60 and 20:80 on N basis), each @ 105 kg N ha^-1 was conducted on timothy during 2008-’11 at Thunder Bay, Ontario. A check (no N) treatment was also kept. Application of N, in all forms, significantly increased the dry matter yield (DMY) of timothy in all the years. Averaged over three years, highest yield increase (2,400 kg ha^-1), as compared to check was registered by 80: 20 blend of urea and ammonium sulphate. DMY of timothy from this blend (4,964 kg ha^-1) was higher than that from urea (4,445 kg ha^-1) or ammonium sulphate (4,585 kg ha^-1). Sulphur in ammonium sulphate could contribute to increased yield from the blend with urea than urea alone. Protein content in timothy from 80:20 blend of urea and ammonium sulphate (12.7 %) equaled that from ammonium sulphate (12.8 %), but was somewhat lower than that with urea (13.2 %). Considering the yield benefit and decreasing sulphur deposition from air, application of part (20 %) N from ammonium sulphate could be recommended for timothy production in northwestern Ontario.

Key words: Timothy, urea, ammonium sulphate, blends of N fertilizers, dry matter yield, and protein content.